I went dull vest, shiny neck. The vest does seem to be a lot less shiny compared to the neck, at least on ESB, although that could be down to heavier weathering. It's just personal preference really since either combination will get you cleared.
I looked through absolutely loads of different samples to get what I felt was the right level of shine and fabric weight. I went with a lightly satinised cotton.
The flight suit is a Bobamaker that I am altering. It isn't quite perfect but the areas of it that fall short are, and I shudder to say this, going to hidden by the flak vest and armour. There; I've said it. Now I feel ashamed.